3
Table 1
scale ratio
Scale mile
(in)
1/25 mile 1/50 mile
1/100
mile
1/200
mile
Z
220
288.000
11.52
5.760
2.880
1.440
In
N
160
396.000
15.87
7.920
3.960
1.980
In
HO
87
728.276
29.132
14.566
7.283
3.641
In
OO
76
833.684
33.348
16.674
8.337
4.168
In
O
48
1320.000
52.8
26.400
13.200
6.600
In
S
64
990.000
39.60
19.800
9.900
4.950
In
G
24
2640.000
105.60
52.800
26.400 13.200
In
TT
120
528.000
21.12
10.560
5.280
2.640
in
Table 2
scale ratio
scale km
(cm)
1/25 km
1/50 km 1/100 km
1/200
km
Z
220
454.55
18.18
9.09
4.55
2.27 cm
N
160
625.00
25
12.50
6.25
3.13 cm
HO
87
1149.43
45.98
22.99
11.49
5.75 cm
OO
76
1315.78
52.62
26.31
13.16
6.58 cm
O
48
2083.33
83.34
41.67
20.83
10.42 cm
S
64
1562.50
62.5
31.25
15.63
7.81 cm
G
24
4166.67
166.66
83.33
41.67
20.83 cm
TT
120
833.33
33.34
16.67
8.33
4.17 cm
The accuracy of the unit depends upon how precisely the
sensors are spaced. For example, for N scale and the 1/100
interval, from table 1, 3.96 inches should be used. 4 inches
will give you about a 1% error in the speed reading. The 1/50
of a mile setting this same measurement error (0.04 in) will
give only a 0.5% speed error. Sensor spacing errors can be
minimized by choosing the longest spacing that is practical for
your layout and scale (for example, 1/50 of a mile in O scale is
over 2 feet which is a bit impractical, while at 5.76 inches it
would be ideal for Z scale).